Define space in the MIPS 'bootinfo' so that boot2 can pass boot-device
information on to loader, and loader can pass it on to the kernel.
As we have a bit more space in our boot area than the average bear, link
against -lstand to get memcpy(), strcmp(), and use strpos() to reduce
hand parsing.  Use our new bootinfo definitions, and for now, don't do
unit numbers (although in the future we may want to).
Add useful debugging output on error to the SD card micro-driver, fix a bug
in SD card error handling.
Use libstand's printf(); trim debugging output.